There should be a rpm macro to define the ruby(api) version so a package can do:

Requires: ruby(api) = %{ruby_api}

or similar.

2012-02-09 vondruch: And how would you treat it? How would you later distinguish that you really like to use different Ruby's api? We could do something like %{ruby_187_api} and %{ruby_193_api}, which would expand to "1.8" and "1.9.1", but this would not avoid the necessity of change in spec when major update of Ruby happens.